TM 5-3820-245-14&P
4.
Start with basic shim pack approximately 0.018. NOTE: BASIC SHIM THICKNESS IS USED AS A STARTING
POINT, MAY BE NECESSARY TO ADD OR SUBTRACT SHIMS FOR DESIRED PRELOAD AND/OR
BACKLASH.
5.
Install pinion tail bearing retainer (Figure 6-4, Item #38) and pinion tail bearing in final drive housing. One
retainer on each side of tail bearing plates hold tail bearing in housing. Install pinion, pinion shaft housing and
shims in final drive housing with the short bolt in its PROPER LOCATION, tighten all bolts to 170 lbs. of torque.
Rotate pinion to check for binding. Remove pinion housing and shims.
6.
Install ring gear on final drive using new bolts, flat washers, and shake-proof lockwasher. With final drive brass
(Item #34) setting on its small end, install large bearing cone using shims as available from previous installation.
Heating of this bearing with steam or in an oven will ease installation of this bearing. Turn main drive over,
install shims as available from previous installation, and install small bearing cone. Heating of this bearing in an
oven or with steam will also ease installation of this bearing.
7.
Lubricate bearings and cones with light coating of oil. Set main drive brass assembly in final drive housing.
Install cover and cover capscrews. Torque capscrews to 90 ft. lbs. before installing pinion and housing sub-
assembly, check main drive for proper preload across bearing. There should be no available free motion and the
preload across bearing should be sufficient to require from 10 to 20 in pounds torque to turn the shaft. If drag is
too much, add to the shims between housing or reduce shims total if too small. With the correct preload on the
final drive brass, install pinion and housing sub-assembly, and shim pack. Make sure the short bolt is in its
proper location. Torque mounting bolts to 90 ft. lbs. Install dial indicator in the pinion splines, check the
backlash at four equal intervals of the output shaft rotation. Backlash should be from 0.005 to 0.008. If the
backlash must be corrected, this is accomplished by removing the final drive housing cover, and the final drive
brass assembly, backlash changes almost equally to ratio as the output gear is moved. Therefore, if backlash
must be increased by 0.005, the shim adjacent to the small bearing should be increased by a like amount,
namely 0.005. In order to do this, the small bearing shim must be removed and reassembled over the final drive
brass. When the final drive brass bearing shim is changed, a compensating change to the housing cover gasket
is generally required to keep the bearing preload proper. Once the backlash has been set in the proper range,
rotate the pinion ten (10) full turns in both directions. Remove the pinion and housing sub-assembly and inspect
the pinion pattern comparing to the example, (see Figure 6-9). The concave side of the pinion is the major load
side and its pattern is NOT CORRECT. The pattern should be adjusted by
PAGE 89
